1. Field of the Invention
The present invention relates to an image recording method and apparatus that produce holographic stereograms having parallaxes both in the horizontal (left and right) directions and vertical (upper and lower) directions and to an image record medium on which the holographic stereograms are recorded.
2. Description of the Related Art
A hologram of a three-dimensional image can be produced using two-dimensional original images of an object taken from different view points. A holographic stereogram is produced, for example, by successively recording many original images of which an object is taken from different observation points as stripe-shaped or dot-shaped elemental holograms on one hologram record medium.
As shown in FIG. 14, a holographic stereogram having parallax information only in the horizontal directions is produced, for example, by an image recording apparatus that records images of which a plurality of original images 101a to 101e of an object 100 successively taken from horizontally different observation points have been processed as stripe-shaped elemental holograms to a record medium 102.
In this holographic stereogram, image information obtained by successively taking an object from different horizontal observation points is successively recorded as horizontally stripe-shaped elemental holograms. Thus, when the user watches the holographic stereogram with both his or her eyes, two-dimensional images that he or she watches with his or her eyes slightly differ. Thus, the user feels parallaxes with the images and watches them as a three-dimensional image. In the following, holographic stereograms may be simply referred to as holograms.
As described above, when stripe-shaped elemental holograms are recorded, a horizontal parallax only (HPO) holographic stereogram having parallaxes only in the horizontal direction is produced. An HPO type holographic stereogram can be printed in a short time and recorded with high quality. There are many demands of recording natural spatial effects not only with horizontal parallaxes but with vertical parallaxes. Although embossed type holographic stereograms have been widely used for forgery prevention of credit cards, they have been easily forged. The embossed type holographic stereograms are being replaced with more advanced volume (Lipman) recording mediums. Since the volume recording mediums allow for recording of vertical parallaxes that are not theoretically represented by the embossed holographic stereograms, there were demands of a recording system that has further improving forgery prevention effects with the vertical parallaxes.
Full parallax (FP) holographic stereograms having parallaxes both in the horizontal and vertical directions have been proposed, for example, in Japanese Patent Application Laid-Open No. HEI 6-266274 and Japanese Patent Application Laid-Open (translation version of PCT international publication) No. 2002-530699.